Sugarcane is the world's largest crop. Brazil is the largest producer of sugarcane in the world. The world demand for sugar is the primary driver of sugarcane agriculture. Sugarcane accounts for about 80% of sugar produced; most of the rest is made from sugar beets. Sugarcane predominantly grows in the tropical and subtropical regions, and sugar beet predominantly grows in colder temperate regions of the world.
The production of sugar (sucrose) from raw sugarcane is well-known. Furthermore, the development of equipment and associated processes for producing sugar from sugarcane stalks has been extensive. Generally, sugar product is produced from a naturally occurring liquid contained within the cells of sugarcane stalks.
In particular, the recovery of sucrose from the cane plant requires the separation of juice from the fibrous material in the structure of the stalk. The tissue inside the rind of the stalk is a matrix of thin-walled parenchyma cells in which are imbedded vascular bundles. Sucrose is present principally in the parenchyma storage cells. These cells are easily ruptured and the most commonly employed methods to extract the juice are by milling or crushing, hot-water extraction, or a combination of these methods. In the hot-water extraction method, cane is typically prepared by knife mills and roller-crusher combinations.
Recently, the Green Power+® technology has been developed by American Process, Inc. based in Atlanta, Ga., United States. Green Power+ technology is capable of extracting hemicellulose sugars and acetic acid from lignocellulosic biomass, including sugarcane bagasse, sugarcane straw, and related feedstocks. In the Green Power+ process, the hemicelluloses are extracted using steam or liquid hot water and then converted to monomer sugars using a catalyst (acids or enzymes). The acetic acid can be recovered in the form of acetic acid or acetate.
Most sugarcane ethanol mills are in remote locations and use the bagasse to generate the necessary steam and power to run the mill and occasionally export to the local grid. It is therefore not viable to divert all the bagasse to the production of cellulosic ethanol. However, the diversion of only the hemicelluloses of the bagasse to the production of cellulosic ethanol is robust and financially attractive proposition, leading to competitive production of cellulosic ethanol. Such an application using the Green Power+ technology can result in incremental cellulosic ethanol production in an existing sugarcane ethanol mill and still allow the mill to produce its steam and power energy needs (possibly an energy surplus).
Further improvements in sugarcane processing are desired. It would be desirable to utilize Green Power+ technology so that hemicellulose sugars and other co-products may be economically obtainable, along with sucrose or fermentation products from the sucrose.